Buyers are always 100% protected when buying on eBay since eBay will step in and refund if you if there are issues and the seller turns out to be a deadbeat (eBay owns PayPal).
I often feel much safer buying from eBay than any other unkown store due to this protection you have. With any other place it's you against them.
Now Suyi at Auberins OTOH is a great guy so I'd have no issues buying from him (and have done so many times in the past).
But if it's up against small online store online that I've never dealt with in the past vs buying from someone else (or even the same seller) off eBay, I choose eBay all the time for the extra safety net.
Now about the PID in question: The only thing it doesn't seem to have is manual mode- useful for the boil kettle. You didn't say how you want to use the PID so I don't know if it matters.
Import duties are fees you may or may not have to pay when you purchase something worth more than about $20-30 from outside your own country (check your customs office for exact details). This PID ships from Hong Kong. For what it's worth, I've bought tons of stuff from HK sellers and they always mark the packages lower in value. I've never paid for import duties on small items like this.